Recently in U.S. Patent Nos. 3,769,301 and 3,907,544 herbicidal compounds of the general formula: ##STR2## where
X is halogen; PA1 n is 1 or 2; PA1 A is, among others, --N--(CO).sub.m --R.sub.4 ; PA1 Y is oxygen or sulfur, PA1 X is chlorine or bromine; and PA1 Y is S or N--CH.sub.3. PA1 I. r is alkyl or alkoxy of 1 or 2 carbon atoms; PA1 Ii. x is chlorine. PA1 A. 2-chloro-N-(2,4-dioxothiazolidin-3-ylmethyl)-N-(2-methylphenyl)acetamide, m.p. 134.degree.-137.degree. C; PA1 b. 2-chloro-N-(2,4-dioxothiazolidin-3-ylmethyl)-N-(2-methoxyphenyl)acetamide, m.p. 188.degree.-191.degree. C.
where
m is 0, 1, or 2; and PA3 R.sub.3 and R.sub.4 together can form a alkylene bridge or 2-5 carbons; and
Were disclosed.
The compounds taught within these patents are active herbicides; the need still exists, however, for herbicides which are more active. The presence of undesired vegetation is very damaging to useful crops such as rice. In the current world situation, wherein food shortages are acute, it is most important not to lose a significant portion of a valuable crop such as rice. The presence of such undesired vegetation results in the loss of a significant portion of such crop. Thus, a need exists for a particularly effective herbicide which will destroy as much of this unwanted vegetation as is possible without causing significant damage to the desired crops, e.g. rice.
According to the instant invention, herbicidal compounds have been discovered which are highly active herbicides and yet cause minimal damage to certain desired crops, e.g. rice.